Optical aspects of Near-Infrared Imager Spectrometer and Polarimeter instrument (NISP)

TL;DR

The paper discusses the optical design and capabilities of the NISP instrument for the upcoming 2.5 m telescope at PRL, highlighting its imaging, spectroscopic, and polarimetric functionalities across near-infrared wavelengths.

Contribution

It presents the optical aspects and design considerations of NISP, a multifaceted near-infrared instrument with advanced imaging, spectroscopy, and polarimetry modes.

Findings

Designed for 0.8-2.5 micron wavelength range

Features a 2K x 2K H2RG detector with 10' x 10' FOV

Includes multi-wavelength imaging-polarimetry with WeDoWo prisms

Abstract

As a Near-IR instrument to PRL's upcoming 2.5 m telescope, NISP is designed indigeniously at PRL to serve as a multifaceted instrument. Optical, Mechanical and Electronics subsystems are being designed and developed in-house at PRL. It will consist of imaging, spectroscopy and imaging-polarimetry mode in the wavelength bands Y, J, H, Ks i.e. 0.8 - 2.5 micron. The detector is an 2K x 2K H2RG (MCT) array detector from Teledyne, which will give a large FOV of 10' x 10' in the imaging mode. Spectroscopic modes with resolving power of R ~ 3000, will be achieved using grisms. Spectroscopy will be available in single order and a cross-dispersed mode shall be planned for simultaneous spectra. The instrument enables multi-wavelength imaging-polarimetry using Wedged-Double Wollaston (WeDoWo) prisms to get single shot Stokes parameters (I, Q, U) for linear polarisation simultaneously, thus increasing the efficiency of polarisation measurements and reducing observation time.